Why the rising tide of video traffic is like nothing you've been told.

Carrier network planners have been scrambling to stay ahead of network capacity demands, which in many cases are exceeding forecasts made only a year ago. Spending on DWDM gear is up 61% from a year ago and up 171% from two years ago, according to Ovum-RHK, which predicts Internet traffic to keep growing at about 40% per year.

But as carriers race to light extra capacity, they are in many ways in the dark about where that capacity demand is headed, especially with the rise of new bit-heavy video services. The steady march of fiber-based broadband is opening floodgates in neighborhoods across the country, and the meteoric rise of YouTube poses new possibilities for network traffic growth curves.

But new data is leading some researchers to question the common assumptions surrounding network traffic trends. They are wondering if fiber pipes really drive dramatic increases in bandwidth usage — and some say Internet traffic growth is actually slowing down.

“I've been telling people in telecom they should start worrying about stimulating traffic as opposed to controlling it,” said Andrew Odlyzko, a professor at the University of Minnesota who researches Internet traffic. The current growth rate “corresponds to practically no revenue increase,” he said.

Down in the guts of telecom networks, the urgency of expansion is apparent. In mid-2006, XO Communications lit a 100 Gb/s intercity optical network to replace leased capacity that had leases expiring. Six months after the company started building that network, it set to work doubling the original capacity. “We blew through it very quickly,” said Randy Nicholas, chief technology officer for XO.